Lubricating oil and lubrication therewith



Patented May 12, 1942 UNITED STATES PATENT. OFFEE LUBRICATING om AND LUBRICATION rncaawrrn Elmer William Cook, New York, N. Y., assignor to Tide Water Associated Oil Company, Bayonne, N. J., a corporation of Delaware No Drawing. Application December 10, 1938, Serial No. 244,976

8 Claims.

This invention relates to mineral oil composiwith resultant oxidation and formation of acids,-

increase in viscosity and increase in carbon residue. These deterioration tendencies are amplified many fold at increasingly higher temperatures. Metals, likewise, seem to increase the susceptibility of petroleum lubricating oils to deterioration of the aforesaid character. It is a primary object of the present invention, therefore, to inhibit or retard the above and other deteriorating influences by the addition to lubrieating and like oils of a small amount of an oilsoluble organic metallic sulfide.

The present application is a continuation-inpart of my copending application Serial No. 158,916, filed August 13, 1937, now Patent No. 2,139,725 issued December 13, 1938, for improvements in Lubricating oil and lubrication therewith; and in one important embodiment the present invention is concerned with lubricants intended for service in the lubrication of internal combustion engines. These now are frequently equipped with bearings comprisingor surfaced with cadmium-silver, cadmium-nickel, copperlead or like alloys having substantially the corrosion susceptibility of the stated alloys. Such harder, higher melting alloys are in certain respects better adapted to the requirements of modern internal combustion engines than the conventional Babbitt metal hearings, in view of greatly increased bearing pressures and the high temperatures which may obtain at bearing surfaces during operation. The mechanical superiority of cadmium-silver and other special alloy bearings is largely offset, however, by a marked susceptibility to corrosion under service conditions by many available lubricating oilsparticularly oils which by nature or refining are of the character generally regarded as superior lubricants by conventional criteria (e. g., high viscosity index, substantially or reasonably free from sludge-forming tendencies, etc.).

Under service conditions the presence of cadmium-silver 'andlike alloys appears to catalyze reactions tending toward lubricant degradation. Such alloys likewise seem to be particularly susceptible to corrosion by lubricants which have undergone deterioration in service. It has been suggested that corrosion of bearing metals in internal combustion engines involves a cyclic action or chain of reactions in the course of which the catalytic effect of the bearing metal accelerates oil deterioration and the products of deterioration in turn attack the bearing surfaces with resultant corrosion thereof.

The invention, however, is concerned with retarding lubricant deterioration and deterioration effects without limitative regard to the foregoing or other theory which may be advanced to explain causes or results. It has been found that organic metallic sulfides comprise a class providing compounds effective to inhibit oil deterioration and deterioration effects. According to the invention, service degradation of oils is retarded and the corrosiveness of motor oils to cadmium-silver and like alloys markedly diminished by dissolving in the oil prior to use small but sufiicient proportions of an organic metallic sulfide inhibitor.- It is, therefore, an object of the invention to improve, and to prepare improved, lubricating oils of petroleum origin by incorporating therein an organic metallic sulfide inhibitor in small but effective proportions. In a special aspect, the invention may be regarded as encompassing a novel method of lubricating bearings surfaced with an alloy having substantially thecorrosion susceptibility of cadmiumsilver, cadmium-nickel or copper-lead alloys by. applying to the bearing surfaces lubricant comprising mineral hydrocarbon oil normally tending to corrode such alloys and having incorporated therein corrosion retarding .proportions of an organic metallic sulfide inhibitor.

Inhibitors according to the invention are compounds conforming to the general formula such groups as alkyl, aryl, aralkyl. allroxy, amino,

hyolroxy, and nitro radicals. inhibitors selected from the defined class need not consist solely of one or another pure organic metallic sulfide, mixtures being efiectlve.

Illustrative of the organic metallic sulfides which may be regarded as encompassed within the scope of the present invention are the following:

Trimethyl arsine sulfide Triethyl arsine sulfide Tribenzyl arsine sulfide Triethyl stibine sulfide Triphenyl stibine sulfide Tribenzyl stibine sulfide Trimethyl stibine sulfide The individual efiectiveness of organic metallic sulfide inhibitors will vary somewhat as might be expected, some being more efleotive than others in given proportions. In general it is preferred to use those having greatest inhibitor efiectiveness at small concentrations.

As indicated hereinbefore, organic metallic sulfide inhibitors have proved markedly efiective in retarding the corrosion of bearing metals by lubricating oils normally corrosive thereto under high temperature service conditions obtaining in internal combustion engines. Concurrent oil deterioration is evidenced by undesirable increases in viscosity, carbon residue, neutralize. tion number and Indiana precipitation number also is retarded in beneficial degree by the use of inhibitors as herein disclosed. Generally, the

circumstances giving rise to the need for inhibitors in motor oil service, particularly the problem of bearing corrosion, include high operating temperatures, for example 300 F.400 F. or even higher in certain localized areas. The present invention provides an adequate overall improvement in lubricants and in lubrication for such service.

Thus it will be seen that the invention supplies inhibitors of broad utility in mineral oil environment. Mineral oils of lubricating viscosity are definitely improved for a wide range of services by the addition thereto of an organic metallic sulfide inhibitor in small but sufilcient proportions to retard oil deterioration and deterioration effects.

The proportion of an organic metallic sulfide inhibitor necessary to accomplish the objects of the present invention is quite small, percentages of the order of 0.05%-0.2% by weight or even less dissolved in mineral lubricating oil exhibit= ing a marked inhibiting effect. Larger proportions within the limit of solubility for a given metallic sulfide may be used if desired but the smaller proportions ordinarily are wholly sumcient and, in the interest of economy, preferable. In the illustrative tests reported hereinafter certain specific proportions of inhibitor were used, but stated percentages herein are not in tended as a limitation upon the contemplated aeearov scope and practice of the invention. The inhibitors may be, and are intended to be, employed in any inhibiting proportion. 4

The tendency of motor oils to corrode bearing metals may be determined by a convenient test which afiords a ready method of obtaining a comparative evaluation of motor oils in the laboratory, In this test method a group of bear ings, ordinarily including at least one each of several of the newer bearing metal alloys (viz: cadmium-silver, cadmium-nickel and copperlead) is supported in a chamber in which air may circulate and the bearing surfaces are ex= posed for a period of 22 hours to a stream of oil sprayed. under pressure continuously upon the corrodible area. The oil is maintained at a tern perature of approximately 335 F. and the spray is so directed as to disperse the oil over the surfaces of the bearings. Means are provided for recirculating the sprayed oil so that a given queu tity is used for a given test, thus simulating service conditions in an engine. The measure of corrosion is taken as the loss in weight of the bearing per unit of exposed corrodible surface.

The test method described above is carried out in the familiar Underwood corrosion apparatus supplied by the Scientific Instrument Company of Detroit, Michigan, in accordance with General Motors specifications.

Results obtained utilizing the foregoing test for comparative evaluation of motor oils with and without an inhibitor according to the invention provide specific illustration of the value and in-- hibiting efliectivcness of organic metallic sulfides. The oil used for the tests was an 'S. A. E. 20 motor oil comprising a blend of well refined parafiinic base stocks and having an A. P. I. gravity of 30.1, Saybolt viscosity at F. of about 300 seconds, Saybolt viscosity at 210 F. of 54 seconds and flash point of 425 F. Inhibitor, when added, was used in an amount of 0.2% by weight based on the oil. During each run cadmium-silver,

cadmium-nickel and copper-lead bearings all were present; and comparative losses in weight per square decimeter due to corrosion were ob served as follows for the respective bearings:

Example A Oil plus triphcnyl arsine Oil Bearing blank Grams Cadmium-silver 7. Cadmium-nickel. Copper-lead No loss No loss No loss Example B 011 plus triphcny! stiblue sulfide Oil Bearing blank Grams Cadmium-silver Cadmium-nickel Copper-lead No loss No loss No loss I claim:

1. Method of lubricating bearing surfaces, at least one of which comprises an alloy having substantially the corrosion susceptibility of cadmium-silver, cadmium-nickel and copperlead alloys, which comprises applying to the bearing surfaces lubricant having incorporated therein, in corrosion inhibiting proportions, a sufficiently oil-soluble organic metallic sulfide.

2. Method of lubricating bearing surfaces, at least one of which comprises an alloy having substantially the corrosion susceptibility of cadmium-silver, cadmium-nickel and copperlead alloys, which comprises applying to the bearing surfaces lubricant having incorporated therein, in corrosion inhibiting proportions, a sufiiciently oil-soluble aryl metallic sulfide.

3. Method of lubricating bearing surfaces, at least one of which comprises an alloy having substantially the corrosion susceptibility of cadmium-silver, cadmium-nickel and copperlead alloys, which comprises applying to the bearing surfaces lubricant having incorporated therein, in corrosion inhibiting proportions, a sufliciently oil-soluble alkyl metallic sulfide.

4. Method of lubricating bearing surfaces, at least one of which comprises an alloy having substantially the corrosion susceptibility of cadmium-silver, cadmium-nickel and copperlead alloys, which comprises applying to the bearing surfaces lubricant having incorporated therein, in corrosion inhibiting proportions, a suificiently oil-soluble organic metallic sulfide whose metallic constituent is one selected from the group consisting of arsenic and antimony,

5. Method of lubricating bearing surfaces, at least one of which comprises an alloy having substantially the corrosion susceptibility of cadmium-silver, cadmium-nickel and copperlead alloys, which comprises applying to the bearing surfaces lubricant having incorporated therein, in corrosion inhibiting proportions, a sufficiently oil-soluble aryl metallic sulfide whose metallic constituent is one selected from the group consisting of arsenic and antimony.

6. Method of lubricating bearing surfaces, at least one of which,comprises an alloy having substantially the corrosion susceptibility of cadmium-silver, cadmium-nickel and copperlead alloys, which comprises applying to the' bearing surfaces lubricant having incorporated therein, in corrosion inhibiting proportions, a sufficiently oil-soluble alkyl metallic sulfide whose metallic constituent is one selected from the group consisting of arsenic and antimony.

7. Method of lubricating bearing surfaces, at least one of which comprises an alloy having substantially the corrosion susceptibility of cadmium-silver, cadmium-nickel and copperlead alloys, which comprises applying to the bearing surfaces lubricant having incorporated therein, in corrosion inhibiting proportions, a sufliciently oil-soluble organic metallic sulfide whose metallic constituent is one selected from the group consisting of arsenic and antimony and whose organic radical is one selected from the group consisting of phenyl and benzyl.

8. Method of lubricating bearing surfaces, at

' least one of which comprises an alloy having 

